Fibrin assembly and formation is related to fibroblast activity, a relationship of importance to wound healing and inflammation. To study this interaction, sophisticated, state-of-the-art physical measurements are required. The basic types of information necessary to characterize these interactions include mass/length ratios of fibrin fibers, diffusion coefficients of both fibrin intermediates and perturbing macromolecules, selective measurement of diffusion in the presence of other interfering macromolecules, of fibroblast and endothelial cells, and rheological assessment of modified fibrin gels. We have developed a variety of light scattering and rheological techniques to permit an orderly means to determine the influence of selected naturally occurring macromolecules, e.g. immunoglobulins, albumin, collagen, leukocyte lysosomal cationic protein, fibronectin, etc. on fibrin assembly. Plasmin digestion of fibrin gels formed with with specific structural characteristics will be studied by Holographic light scattering, HRS. In addition, new technology including the combination of electrophoretic light scattering (ELS) and HRS, has been developed to investigate the interaction of fibrin with fibroblasts and endothelial cells. Physical properties of fibrin receptors on fibroblast and endothelial cell surfaces will be studied by several different light scattering methods. Fibroblast function will be related to specific structural requirements of fibrin, namely fiber diameter, gel rigidity, fiber density and the presence of other macromolecules, e.g. fibronectin. This information will be highly useful in a variety of clinical settings related to host defense mechanisms, namely the inflammatory response and wound healing.